The present invention relates to method and apparatus for providing an alignment of elements such as optical fibers in a predetermined array to a predetermined tolerance value.
Fiberoptics is used in the communication industry for high levels of data transport. As a result, optical fibers need to be coupled with precision to semiconductors, detectors, and mirrors in arrays.
A method for obtaining precision accuracies is to use photolithography to image a mask of array openings on a substrate such as silicon. Silicon is chosen because it has a low thermal coefficient equal to that of silicon substrates that optical fibers match into. Using a photolithographic mask, the openings of the array are etched in the silicon wafers. For small openings such as those for 125 micrometer diameter single mode optical fibers which are nominally 124-126 micrometers in diameter, the cross-section of the etched opening in the silicon substrate is nominally 126 micrometers. There can be a variation in the size of the opening during etching or laser drilling. As a result, the openings can have variations in cross-section and, consequently, cause inaccuracies in the placement of optical fibers in the plane of the substrate.
It is desirable to provide an array of elements, such as optical fibers, in which alignment (i.e., center-to-center spacings of the elements) of an exemplary tolerance value of xc2x12.0 micrometers is repeatedly achievable and to have registration techniques to achieve such alignment accuracy for the elements.
The present invention is directed to method and apparatus for providing an alignment of an array of elements such as optical fibers to a preselected center-to-center tolerance value.
From a first apparatus aspect, the present invention is directed to an array apparatus comprising a primary substrate and a plurality of N elements. The primary substrate has sufficient structure to support an array of N spaced-apart elements and defines a plurality of N apertures which each extend therethrough from a first surface to a second opposing surface of the primary substrate with a cross-section of each of the N apertures being greater than a cross-section of an optical fiber and having a center that is aligned to a preselected tolerance value which is required for the array of elements. A smallest cross-section of each of the apertures is such that when the plurality of elements are inserted through their primary substrate apertures they have limited variations that facilitate spacings between adjacent elements that are within the preselected tolerance value. Each of the elements passes through one of the N apertures in the primary substrate and rests against the same one of a group consisting of a predetermined point and a predetermined side of its associated aperture such that the plurality of N elements are aligned within the preselected tolerance value.
From a second apparatus aspect, the present invention is directed to an optical fiber array apparatus comprising a primary substrate and a plurality of N optical fibers. The primary substrate has sufficient structure to support an array of N spaced-apart optical fibers and defines a plurality of N apertures which each extend therethrough from a first surface to a second opposing surface of the primary substrate with a cross-section of each of the N apertures being greater than a cross-section of an optical fiber and having a center that is aligned to a preselected tolerance value which is required for the array of optical fibers. A smallest cross-section of each of the apertures is such that when the plurality of optical fibers are inserted through their primary substrate apertures they have limited variations that facilitate spacings between adjacent optical fibers that are within the preselected tolerance value. Each optical fiber comprises a cladding layer surrounding an optical core, and when each optical fiber is inserted through its associated aperture in the primary substrate it is registered by a spring-like force in the optical fiber against one of a group consisting of a predetermined point and a predetermined side of its associated aperture which is the same for each of the plurality of N optical fibers and their associated apertures such that the plurality of N optical fibers are aligned within the preselected tolerance value.
From a third apparatus aspect, the present invention is directed to apparatus for registering a plurality of optical fibers in an optical fiber array comprising a primary substrate and a directing arrangement. The primary substrate has sufficient structure to support an array of N spaced-apart optical fibers and defines a plurality of N apertures in a predetermined pattern which each extend therethrough from a first surface to a second opposing surface of the primary substrate where each of the N apertures comprises a cross-section which is greater than a cross-section of an optical fiber, the apertures having centers that are aligned to a preselected tolerance value which is required for the array of optical fibers. A smallest cross-section of each of the apertures is such that optical fibers inserted through the primary substrate apertures have limited variations that facilitate spacings between adjacent optical fibers placed in the apertures being within the preselected tolerance value. The directing arrangement directs each of the plurality of N optical fibers at a predetermined angle towards the primary substrate so that each optical fiber is curved with a spring-like action after threading into the associated aperture in the primary substrate such that the optical fiber is registered against one of a group consisting of at least one of a predetermined point and a predetermined side of the associated aperture in the primary substrate.
From a fourth apparatus aspect, the present invention is directed to an array apparatus comprising a primary substrate and a plurality of N elements. The primary substrate has sufficient structure to support an array of N spaced-apart elements and defines a plurality of N apertures which each extend therethrough from a first surface to a second opposing surface of the primary substrate with a cross-section of each of the N apertures being greater than a cross-section of an element and having a center that is aligned to a preselected tolerance value which is required for the array of elements. A smallest cross-section of each of the apertures is such that when the plurality of elements are inserted through their primary substrate apertures they have limited variations that facilitate spacings between adjacent elements that are within the preselected tolerance value. When each element is inserted through its associated aperture in the primary substrate it is registered, by a spring-like force in the element, against one of a group consisting of a predetermined point and a predetermined side of its associated aperture which is the same for each of the plurality of N elements and their associated apertures such that the plurality of N elements are aligned within the preselected tolerance value.
From a fifth apparatus aspect, the present invention is directed to array apparatus comprising a relatively thick primary substrate and a relatively thin first layer. The relatively thick primary substrate has sufficient structure to support an array of N spaced-apart elements and has first and second opposing surfaces and defines a plurality of N primary substrate apertures which each extend therethrough from the first surface to the second surface with a cross-section of each of the N substrate apertures being greater than a cross-section of an element such that one element can be passed through in each of the N primary substrate apertures. The relatively thin first layer, which has insufficient structure by itself to support an array of N spaced-apart elements, engages the second surface of the primary substrate and defines N apertures therethrough with centers thereof being aligned to a preselected tolerance value which is that required for the array of elements. The smallest cross-section of each of the first layer apertures is less than the smallest cross-section of each of the primary substrate apertures and greater than the cross-section of an element to be placed therein, each first layer aperture being within a footprint of one of the primary substrate apertures. When each element is inserted through its associated aperture in each of the primary substrate and the relatively thin first layer it is registered against one of a group consisting of a predetermined point and a predetermined side of its associated aperture which is the same for each of the plurality of N elements and their associated apertures such that the plurality of N elements are aligned within the preselected tolerance value.
From a first method aspect, the present invention is directed to a method of registering a plurality of N elements to a preselected value in an array. The comprises the steps of: forming a primary substrate having sufficient structure to support an array of N spaced-apart elements and defining a plurality of N apertures in a predetermined pattern across the primary substrate, wherein each aperture extends therethrough from a first surface to a second opposing surface of the primary substrate, has a cross-section at its narrowest point which is greater than a cross-section of an element, and has a center which is aligned to a preselected tolerance value for the apertures which is required for the array of elements, the smallest cross-section of each of the apertures being such that elements inserted through the primary substrate apertures have predetermined limited side movement variations; and inserting each of the plurality of N elements through one of the N apertures in the primary substrate such that each of the N elements rests against at least one of a group consisting of a predetermined point and a predetermined side of its associated aperture such that the plurality of N elements are aligned within the preselected tolerance value.
From a second method aspect, the invention is directed to a method of registering a plurality of N optical fibers to a preselected value in an optical fiber array. The method comprises the steps of: (a) forming a primary substrate having sufficient structure to support an array of N spaced-apart optical fibers and defining a plurality of N apertures in a predetermined pattern across the primary substrate, wherein each aperture extends therethrough from a first surface to a second opposing surface of the primary substrate, has a cross-section at its narrowest point which is greater than a cross-section of a cladding layer of an optical fiber, and has a center which is aligned to a preselected tolerance value for the apertures which is required for the array of optical fibers, the smallest cross-section of each of the apertures being such that optical fibers inserted through the primary substrate apertures have predetermined limited side movement variations; (b) directing each of the plurality of N optical fiber at a predetermined angle towards the primary substrate from a directing arrangement; and (c) causing each optical fiber to be curved with a spring-like action into a predetermined angular direction to the first surface of the primary substrate for threading through the associated aperture in the primary substrate, and be registered against one of a group consisting of a predetermined point and a predetermined side of its associated aperture by the spring-like action when the optical fiber is threaded through the associated aperture in the primary substrate.
From a third method aspect the invention is directed to a method of forming an array apparatus which supports N spaced-apart elements to a preselected tolerance value. The method comprises the steps of: (a) forming a primary substrate having sufficient structure to support an array of N spaced-apart elements and defining a plurality of N apertures in a predetermined pattern across the primary substrate, wherein each aperture extends therethrough from a first surface to a second opposing surface of the primary substrate, has a cross-section at its narrowest point which is greater than a cross-section of an element, and has a center which is aligned to a preselected tolerance value for the apertures which is required for the array of elements, the smallest cross-section of each of the apertures being such that elements inserted through the primary substrate apertures have predetermined limited side movement variations; (b) directing each of the plurality of N elements at a predetermined towards the primary substrate from a directing arrangement; and (c) causing each element to be curved with a spring-like action into a predetermined angular direction to the first surface of the primary substrate for threading through the associated aperture in the primary substrate, and be registered against one of a group consisting of a predetermined point and a predetermined side of its associated aperture by the spring-like action when the element is threaded through the associated aperture in the primary substrate.
The invention will be better understood from the following more detailed description taken with the accompanying drawings and claims.